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Prestressed Concrete Structures
UNIT- I
INTRODUCTION – THEORY AND BEHAVIOUR
9
Basic concepts – Advantages – Materials required – Systems and methods of prestressing –
Analysis of sections – Stress concept – Strength concept – Load balancing concept – Effect of
loading on the tensile stresses in tendons – Effect of tendon profile on deflections – Factors
influencing deflections – Calculation of deflections – Short term and long term deflections Losses of prestress – Estimation of crack width.
Introduction:
The idea of prestressed concrete has been around since the latter decades of the 19th century, but
its use was limited by the quality of the materials at the time. It took until the 1920s and ‘30s for
its materials development to progress to a level where prestressed concrete could be used with
confidence. Freyssinet in France, Magnel in Belgium and Hoyer in Germany were the principle
developers.
The idea of prestressing has also been applied to many other forms, such as:
Force-fitting of metal bands on wooden barrels
The metal bands induce a state of initial hoop compression, to counteract the hoop tension
caused by filling of liquid in the barrels.
Pre-tensioning the spokes in a bicycle wheel
The pre-tension of a spoke in a bicycle wheel is applied to such an extent that there will
always be a residual tension in the spoke.
Force-fitting of metal bands on wooden barrel
M.P.Karthik, AP/Civil, SSMIET, Dgl
Pre-tensioning the spokes in a bicycle wheel
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